Sutton has often observed the face of the _Macacus rhesus_,
when much enraged, growing red. As he was mentioning this to me,
another monkey attacked a _rhesus_, and I saw its face redden as plainly
as that of a man in a violent passion. In the course of a few minutes,
after the battle, the face of this monkey recovered its natural tint.
At the same time that the face reddened, the naked posterior part
of the body, which is always red, seemed to grow still redder;
but I cannot positively assert that this was the case.
When the Mandrill is in any way excited, the brilliantly coloured,
naked parts of the skin are said to become still more vividly coloured.

With several species of baboons the ridge of the forehead projects
much over the eyes, and is studded with a few long hairs,
representing our eyebrows. These animals are always looking
about them, and in order to look upwards they raise their eyebrows.
They have thus, as it would appear, acquired the habit of frequently
moving their eyebrows. However this may be, many kinds of monkeys,
especially the baboons, when angered or in any way excited,
rapidly and incessantly move their eyebrows up and down,
as well as the hairy skin of their foreheads.[15] As we associate
in the case of man the raising and lowering of the eyebrows
with definite states of the mind, the almost incessant movement
of the eyebrows by monkeys gives them a senseless expression.
I once observed a man who had a trick of continually raising
his eyebrows without any corresponding emotion, and this gave
to him a foolish appearance; so it is with some persons who keep
the corners of their mouths a little drawn backwards and upwards,
as if by an incipient smile, though at the time they are not
amused or pleased.

A young orang, made jealous by her keeper attending to another monkey,
slightly uncovered her teeth, and, uttering a peevish noise like _tish-shist_,
turned her back on him. Both orangs and chimpanzees, when a little
more angered, protrude their lips greatly, and make a harsh barking noise.
A young female chimpanzee, in a violent passion, presented a curious
resemblance to a child in the same state. She screamed loudly with widely
open mouth, the lips being retracted so that the teeth were fully exposed.
She threw her arms wildly about, sometimes clasping them over her head.
She rolled on the ground, sometimes on her back, sometimes on her belly,
and bit everything within reach. A young gibbon (_Hylobates syndactylus_)
in a passion has been described[16] as behaving in almost exactly
the same manner.

The lips of young orangs and chimpanzees are protruded,
sometimes to a wonderful degree, under various circumstances.
They act thus, not only when slightly angered, sulky,
or disappointed, but when alarmed at anything--in one instance,
at the sight of a turtle,[17]--and likewise when pleased.
But neither the degree of protrusion nor the shape of
the mouth is exactly the same, as I believe, in all cases;
and the sounds which are then uttered are different.
The accompanying drawing represents a chimpanzee made sulky
by an orange having been offered him, and then taken away.
A similar protrusion or pouting of the lips, though to a much
slighter degree, may be seen in sulky children.

[15] Brehm remarks (`Thierleben,' s. 68) that the eyebrows of the _Inuus
ecaudatus_ are frequently moved up and down when the animal is angered.

Many years ago, in the Zoological Gardens, I placed a looking-glass
on the floor before two young orangs, who, as far as it was known,
had never before seen one. At first they gazed at their own images
with the most steady surprise, and often changed their point of view.
They then approached close and protruded their lips towards the image,
as if to kiss it, in exactly the same manner as they had previously done
towards each other, when first placed, a few days before, in the same room.
They next made all sorts of grimaces, and put themselves in various
attitudes before the mirror; they pressed and rubbed the surface;
they placed their hands at different distances behind it; looked behind it;
and finally seemed almost frightened, started a little, became cross,
and refused to look any longer.